As I said, Someone else told me I should "Invent" a better deraileur guard. I was only fulfilling a request. I built lots of fairings, and someone said I should make a deraileur gaurd, in addition to the fairings. It is kind of a fairing, if you define a fairing as a "protective shield" .
I'm also thinking about chain-guards. Maybe a full length chain guard could be attached to the top of the deraileur guard, perhaps with two screws?
Maybe if I take my rear wheel off, to change a tube, and the bike falls off the park-bench, the deraileur guard will protect the deraileur from the ground?
Maybe I could be running a full-service LBS someday, and someone will walk in , lay $7.00 on the counter, and buy a deraileur guard?